Controllable Liquid Crystal Micro Tube Laser

This study demonstrates controllable random lasing emissions in a dye-doped nematic liquid crystal (DDNLC)-infiltrated microcapillary. The emission wavelength of the micro tube laser can be adjusted by changing the focusing position of the pumped pulses on the center or the periphery of the liquid crystal region of the microcapillary. In addition, with doping azo-dyes in the DDNLC of the micro tube laser, optical controllability of the lasing intensity and wavelength can be further achieved. The controllable micro tube laser may find highly widespread photonic applications in multicolor emitting sources, and vibration and UV sensors.

A hybrid random laser using dye with self-organised GaN nanorods

Self-organized GaN nanorods with population densities ranging between 0.1 and 0.5 m- 2 and average heights in the range 1.7 to 16.5 µm, prepared by metal-organic chemical vapor deposition, were used as scattering centres for random lasing by incorporating Rhodamine 6G liquid dye solutions as the gain media. A lasing threshold as low as 11.3 J/cm2 was obtained from samples with nanorod density above 0.3 m-2. The threshold depended on the nanorod density and diameter, but not the nanorod height. Lasing emission was observed at multiple angles, a clear indication of random lasing.

Raman random lasing in Ba(NO3)2 powder

Random lasing in Raman active material – barium nitrate powder – has been registered in two temporal regimes: nanosecond and picosecond. Stimulated Raman scattering (SRS) in Ba(NO3)2 for picosecond excitation has been shown to have much lower threshold and spectrum containing more components than for nanosecond excitation opposite to the case of a bulk medium. In picosecond regime SRS intensity increased with temperature decreasing and redistributed in favor of the higher order components. SRS pulse duration in picosecond regime was estimated to be in the range 16.5-22 ps. High conversion efficiency of SRS in barium nitrate powder in picosecond regime and its larger stability under laser impact than for bulk samples gives possibility to use it as an active material in Raman converters.